Life cycle assessment (LCA) of a novel geothermal-based multigeneration system using LNG cold energy- integration of Kalina cycle, stirling engine, desalination unit and magnetic refrigeration system

Abstract

A comprehensive and detailed investigation is conducted on a novel multigeneration system developed for Minab city (as a case study) in terms of thermodynamic, economic and environmental aspects. The system utilizes geothermal energy source to simultaneously generate four useful commodities: 36 ton/h pure water, 7774 kW net electricity, 354 ton/h hot water (at 77 °C), and 45 ton/h cold water (at 5 °C). The integrated system consists of four subsystems (Kalina cycle, Stirling engine, magnetic refrigeration system and desalination unit). The process simulation and exergetic evaluation are conducted by Aspen HYSYS V 11 and MATLAB software, respectively. The whole system is 42.95% efficient in terms of exergy and exergy destruction rate is 11382 kW. A sensitivity/3D analysis is also conducted to investigate the mutual interactions among exergy destruction, costs and environmental impact of each component. The exergoeconomic analysis and life cycle assessment conclude that heat exchanger HX-8 should be re-designed to improve the cost-affectivity and decline the negative environmental impact of the designed integrated energy conversion system. A comparison between the proposed multigeneration system and four other geothermal energy based systems consisting of LNG regasification sub-unit shows a significantly higher exergy efficiency and lower cost flow rate of product.